Field
The disclosure relates to a powder for powder blasting with a powder-jet device or a powder mixture for powder blasting with a powder-jet device as described, for example, in EP 1 159 929. Furthermore, the disclosure relates to the use of such a powder and powder mixture, respectively, for the preparation of an agent or material for the powder-jet treatment, especially the powder-jet cleaning of tooth surfaces, preferably tooth root surfaces and dentine.
Related Art
FIG. 1 shows a dental abrasive spraying device disclosed in EP 1 159 929, incorporated by reference. It can be used not only with conventional tap water from a water supply (12), but also with other fluids. A dental abrasive spraying device has a hand-piece (4) nozzle for spraying a dental powder contained in a reservoir (1), together with a carrier gas and a fluid aiding mixing of the powder with the carrier. There are two separate pressure feeds (3,6). Pressurized air comes from the feed (6). A feed (2) supplies pressurized air to swirl the powder in reservoir (1). The swirled powder is led through line (3) to the nozzle (4), where additional air arrives through line (6′) and liquid through line (7). In the device: (a) there is an exchangeably-fixed separate container (10) storing a rinsing liquid which can be supplied separately or together with the water, powder and carrier gas to the nozzle; (b) a branch-line (7) is connectable via a valve (8) to container (10) to allow the liquid to be fed to the nozzle; and (c) there is a suction pump (9) upstream of the valve (8). This device can supply either liquid from line (7), or air from line (6′), to be mixed with the air/powder mixture from line (3).
Also of background interest, disclosing relevant methods and equipment, are U.S. application Ser. No. 11/956,596 filed Dec. 14, 2007, now U.S. Pat. No. 7,762,812, Issued Jul. 27, 2010, and U.S. application Ser. No. 12/047,869 filed Mar. 13, 2008, now U.S. Pat. No. 7,980,923, Issued Jul. 19, 2011, both incorporated by reference.
Powders of background interest are already known from U.S. Pat. No. 3,882,638 or U.S. Pat. No. 4,174,571, whereas the further development of the second mentioned document aims at the provision of particularly gentle powders like glutamate or sodium gluconate being less abrasive in comparison to the hitherto known powders of sodium bicarbonate or Iceland spar, and hence will, to a lesser extent, adversely affect sensitive surfaces, like e.g. tooth root surfaces, but also dental enamel surfaces. Preferred grain sizes range from 140 μm to 200 μm, in case of stronger abrasively affecting powders they also range from 20 μm to 70 μm.
When treating sensitive tooth surfaces, like root dentine or others less strongly mineralized tooth surfaces, with a powder-jet device, it is recommended using powders with a density of no more than 2.0 g/cm3 and a mean grain size of no more than 45 μm. WO 00/53154 discloses such particularly gentle powders for the cleaning of subgingival tooth surfaces, like e.g. root dentine. U.S. Pat. No. 6,126,444 discloses the same, wherein sensitive, in particular subgingival tooth root surfaces were treated with a powder consisting of e.g. crystalline cellulose with a mean grain size of 6, 15, 20, 50 or also 120 μm; and the cleaning efficiency is similarly good as the one obtained when using a powder consisting of sodium bicarbonate, whereas the abrasion of root dentine is considerably less. Whereas U.S. Pat. No. 6,126,444 discloses water insoluble agents, WO 00/53154 discloses water soluble agents like amino acids, sugar or organic acids and the salts thereof, which have the advantage that the powder dissolves in water upon application to the tooth and particularly does not gather in the gingival pockets, where water insoluble agents cause an unpleasant feeling and might possibly even lead to an infection of the gingival pocket or the gingiva. These powders, however, have the disadvantage that, due to one or several grinding and sieving steps, the preparation or manufacturing thereof is expensive and laborious.
Whereas powders consisting of smaller particles have a lower impulse when hitting the tooth surface, and hence abrade less material, the same applies to lighter agents or materials which also have a lower impulse and therefore abrade less material. From U.S. Pat. No. 6,126,444, however, it is evident that powders with a smaller mean grain size obtain similarly good cleaning effects as do powders with larger mean grain sizes. Therefore, neither grain size nor density alone, give information about the powder—in case of an almost similarly good cleaning efficiency—having a stronger or weaker abrasive effect on the tooth surface.
U.S. Pat. No. 5,810,587 discloses another composition for cleaning sensitive tooth surfaces by means of powder-jet devices, wherein, on the one hand, a good cleaning result for the removal of tooth deposit/dental plaque is to be obtained, and, at the same time, an abrasiveness as slight as possible is to be obtained when impinging upon sensitive tooth surfaces. U.S. Pat. No. 5,810,587 recommends using very finely particled materials which are put together to larger “snowballs” and burst upon hitting the tooth surface. Particles ranging in size from 0.01 to 5 μm are formed to larger spheres having dimensions from 10 to 200 μm and breaking apart when they impinge upon the tooth surface. Gibbsite is recommended as raw material.
Substantially, five factors are decisive for the abrasiveness of a powder used for powder blasting. Apart from particle speed, hardness and crushing resistance of the particles, the surface condition and the mass are also decisive. In case of equal mass, large particles with a lower density have almost the same abrasiveness as smaller particles with a higher density. Smaller particles, however, can be used or processed suboptimal in the known powder-jet devices. Generally, such a powder is present in a powder chamber as is shown in EP 1 159 929. Air is blown into said powder chamber, to disperse the powder, wherein the resulting air/powder mixture is fed to a nozzle, to which also water is supplied in general by a separate supply line. At the nozzle end, the air/powder mixture, surrounded by a water jet, exits and impinges upon the tooth surface which is generally arranged at a distance of 1 mm and 5 mm from the nozzle outlet.
From U.S. Pat. No. 4,174,571, it is known to use water-soluble powders that are considered by humans as not having an unpleasant taste. Agglutination inside the powder chamber should also be avoided, why the powder should also not be hygroscopic. This property can also be improved by adding further finely particled substances, like pyrogenic silica.
Further criteria for the selection of suitable jet means are mixing and flight characteristics of the used particles. Upon swirling in the powder chamber, care has to be taken that a constant loading of the outgoing airstream takes place, independent of the amount of powder filled into the powder chamber. This can only be ensured when the powder is uniformly stirred by the airstream and when the pourability, for example, is restricted by the formation of densified areas. Smaller particles tend more to form such densified area than larger particles which, due to their mostly larger mass, are often less suitable for being stirred by the airstream. In addition, the miscibility depends on the agent used. At the same time, it should be possible that the powder be processed by the used powder-jet devices, and the preparation or manufacturing of the powder should be as cost-efficient as possible.
Furthermore, a powder for powder blasting should have a corrosion tendency as low as possible and wear out the jet nozzle as little as possible. It should be possible to manufacture the powder, in the preferred size, preferably directly and without requiring further milling processes and the powder should be eudermic. The powder should be well tolerated by humans and, if possible, have an acceptable taste. In order to shorten or avoid costly and time-consuming applications procedures, the powder should preferably have few side effects and a good digestibility.